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In the absence of sunlight, caves harbor a great diversity of microbial colonies to extensive biofilms with different sizes and colors visible to the naked eye. One of the most widespread and visible types of biofilm are those with yellow hues that can constitute a serious problem for the conservation of cultural heritage in many caves, such as Pindal Cave (Asturias, Spain). This cave, declared a World Heritage Site by UNESCO for its Paleolithic parietal art, shows a high degree of development of yellow biofilms that represents a real threat to the conservation of painted and engraved figures. This study aims to: 1) identify the microbial structures and the most characteristic taxa composing the yellow biofilms, 2) seek the linked microbiome reservoir primarily contributing to their growth; 3) seed light on the driving vectors that contribute to their formation and determine the subsequent proliferation and spatial distribution. To achieve this goal, we used amplicon-based massive sequencing, in combination with other techniques such as microscopy, in situ hybridization and environmental monitoring, to compare the microbial communities of yellow biofilms with those of drip waters, cave sediments and exterior soil. The results revealed microbial structures related to the phylum Actinomycetota and the most characteristic bacteria in yellow biofilms, represented by the genera wb1-P19, Crossiella, Nitrospira, and Arenimonas. Our findings suggest that sediments serve as potential reservoirs and colonization sites for these bacteria that can develop into biofilms under favorable environmental and substrate conditions, with a particular affinity for speleothems and rugged-surfaced rocks found in condensation-prone areas. This study presents an exhaustive study of microbial communities of yellow biofilms in a cave, which could be used as a procedure for the identification of similar biofilms in other caves and to design effective conservation strategies in caves with valuab

La Cueva del Pindal (Ribadedeva, Asturias) y su arte rupestre paleolítico forman parte de la Lista del Patrimonio Mundial de la UNESCO desde 2008. Actualmente está abierta al público con visitas limitadas y en ella se desarrolla un proyecto de investigación sobre actividad microbiana en ecosistemas naturales subterráneos y su aplicación al diseño de estrategias de conservación. El sistema kárstico del Pindal se desarrolla en un macizo calcáreo modelado en forma de terrazas marinas (rasas), situadas entre 30 y 68 metros s.n.m que constituyen el área de captación hídrica preferente y en las que se observan numerosas estructuras exokársticas tipo dolina y poljé. Sobre una de las dolinas, situada casi en la vertical de la cavidad, se instaló una explotación ganadera en 1995. El 23 de octubre de 2019 tras un episodio extremo de precipitaciones (209 l/m2) se produjo una fuerte acumulación de agua en la dolina y una entrada masiva de agua y sedimentos en la cueva. El 31 de octubre se realizó un muestreo específico para conocer los cambios provocados en el ecosistema subterráneo. La inundación provocó un fuerte incremento de materia orgánica, nitrógeno, fósforo y potasio disponibles en los sedimentos y modificaciones muy significativas en la composición de las comunidades microbianas presentes en los sedimentos: aparición de nuevos filos bacterianos (Firmicutes y Bacteroidetes), incluyendo grupos de bacterias patógenas oportunistas (Corynebacterium, Thauera, Clostridiales) y la casi total desaparición de otros (Rokubacteria y Nitrospirae). Los resultados confirman que el agua y sedimentos arrastrados al interior de la cueva en la inundación fueron acompañados de residuos procedentes de la explotación ganadera, demostrando el alto grado de vulnerabilidad de este tipo de ambientes. Tras el estudio e informe correspondiente, la actividad ganadera cesó en 2021 y continúa el estudio de las poblaciones microbianas para conocer su evolución a medio-largo plazo.

Along the northern littoral of the Iberian Peninsula, from Cuerres (Asturias) to Oyambre (Cantabria) there are caves, such as El Pindal (World Heritage List). Two geomorphologic maps have been prepared: a general scaled 1:25000, and a detail one of the cave, with erosional and depositional landforms geomorphologic units. A relative Quaternary chronology for the depositional landforms, uses colour spots. Marine morphologies suitable for determining past sea-level positions were surveyed to identify the elevation of past high-stands and reconstructing paleo-shorelines. As a result, the study of seven erosional surfaces (rasas) in quartzites and six on limestones led to reconstructing a general sequence between 275–120 m and 90–1 m above sea level (a.s.l.) respectively. Around the El Pindal cave there are four rasas cut on quartzites (171–160 m) and four cut on limestone (65–32 m). Other additional indicators of paleoshorelines are: 24–25 m entrance to the El Pindal cave, 20–21 m lower Pindal, 15–17 m marine terrace, 9–10 m shelter, 2–3 m notches and 0–1 m present rasa.Considering the elevation rates for the various rasas, an estimated value of 0.066 mm/y as the most probable, it is concluded that the beginning of Quaternary lays at 172 m a.s.l., MCIN/AEI/10.13039/501100011033, Depto. de Geodinámica, Estratigrafía y Paleontología, Fac. de Ciencias Geológicas, TRUE, pub

“Rare actinobacteria” are non-Streptomyces actinobacteria whose isolation frequency is much lower than Streptomyces strains, commonly isolated by conventional methods [1][2]. Tiwari and Gupta [3][4] reported 120 new genera of “rare actinobacteria” in the first decade of the 21th century. A total of 40 out of 120 genera were isolated from soils, with comparatively lower percentages from other environments: marine and freshwater sediments, marine animals, plants, buildings, etc. A few reports included the rare genera Actinomadura, Nonomuraea, Micromonospora, Streptosporangium, Nocardiopsis, and Pseudonocardia as the most frequent in diverse environments [5][6][7][8][9]. It is noteworthy an abundance of “rare actinobacteria” in extreme environments, as exemplified in Atacama [7] and other deserts [10][11][12][13]. However, Crossiella has not been included among “rare actinobacteria” thus far. Researchers have found that Crossiella is an abundant genus in most studied Spanish caves, whether they are gypsum, karstic or volcanic [14][15][16][17][18][19][20][21], and in other terrestrial and aquatic environments., Texto completo disponible en: https://encyclopedia.pub/entry/45605

Rull cave is a karstic cave located in Vall d’Ebo (Alicante, Southeast of Spain) developed in massive Miocene conglomerates and Cretaceous limestones. Processes in soil above Rull cave and outdoor atmosphere directly influence the underground environment of the cave. Continuous and discrete monitoring of cave atmosphere and soil (from 2012 to 2022) allows to characterise the spatial distribution and temporal variations of the gaseous concentration (222Rn and CO2) and understand the relationship between the processes which occurred in the 3-component system (soil-cave-atmosphere). Besides the presence of visitors, Rull cave maintains stable values of mean temperature (16.2 °C) and relative humidity (97.6%). In an annual cycle the cave presents two different gaseous stages (stagnation and ventilation). Maximum average values of CO2 and 222Rn concentration are reached within the stagnation stage, in the warmest period of the year. On the contrary, in the ventilation stage (in the coldest months) the cave reaches the lowest concentrations in its inner atmosphere. For the study period, daily average CO2 and 222Rn concentrations are 2008 ppm and 1745 Bq/m3, respectively. Results show that the dynamics of 222Rn and CO2 in the cave air follow different patterns defined by the complex relationships between external and internal factors. Findings from this study provide substantial information about the environmental situation of the cave atmosphere in terms of air quality for visitors and workers.

Pindal Cave (Asturias, Spain) and its Paleolithic art have been part of the UNESCO World Heritage List since 2008. The importance of this Paleolithic art led to a research project that deals with deciphering the relationships between environmental conditions and microbial activity in natural underground ecosystems and its application to the design of conservation strategies. The Pindal karstic system develops in a calcareous massif (Carboniferous) modeled in the form of an erosional marine terrace (rasa) by coastal morphogenetic processes. This marine terrace level is located at an elevation of 30-68 meters above current sea level and constitutes the preferred catchment area for runoff water from another higher level (140-170 m) developed on quartzite layers with very low permeability (Ordovician). The cave is the main endokarstic feature of the system. On the surface of the 30-68 m rasa there are numerous exokarstic structures of sinkhole and polje type. On one of the sinkholes, located almost vertically to the cave, a cattle farm was installed in 1995. Between October 19 and 23, 2019, an extreme episode of rainfall occurred in the area with a cumulative total of 209 l/m2. This event caused a strong accumulation of water in the aforementioned sinkhole that finally collapsed, flooding the cave for several days. Immediately after the cave had been drained, environmental measurements and sediment samplings were carried out at various points in order to determine the changes caused in the underground ecosystem. In the most affected area by the flood, changes in humidity and temperature of air and sediments were recorded for several months. Biogeochemical data indicated that the sediments deposited as a result of the flooding presented high values of available organic matter, nitrogen, phosphorus and potassium, much higher than those of the innermost areas did not directly affect by the flooding. The comparative microbiological study of sediment samples revealed that th

Arenaza Cave is located in Vizcaya (N Spain) and contains important Palaeolithic rock art representations. This cave belongs to an active karstic system developed on Lower Cretaceous limestones, mainly consisting of micrites and biomicrites with abundant pyrite moulds. The paintings are made directly on the host rock or on thin stalagmitic calcite crusts. Cretaceous limestones in this area contain important iron ore deposits, which have been mined by subsurface and surface-mining methods since the beginning of the 20th century. Mining activities have induced significant changes in the karstic drainage pattern and in the endo and exokarstic morphologies of the Arenaza karstic system, directly affecting the state of conservation of the prehistoric paintings. Thus, in addition to natural process of deterioration, the enlargement of the limestone fissure system as a result of blasting-induced vibrations seems to be the responsible for changes in the rates of water-rock interactions and of the formation of botryoidal gypsum concretions on the rock surface. The final result is the activation and acceleration of detachment processes and the increase of irreversible deterioration processes in the cave.

Understanding the dynamics and spatial distribution of gases in the subterranean atmospheres is essential to increase the reliability of carbon balances in karst ecosystems or the paleoclimate reconstructions based on cave deposits. This scientific information is also very valuable for cave managers to ensure the safety of visitors and the conservation of the subterranean heritage. Through a comprehensive monitoring of the main air parameters in a shallow temperate cave, we decipher the physical drivers and mechanisms involved in the CO2 and radon exchange between the cave and the outer atmosphere, and how this process is triggered by the changes of local weather. Our results reveal that the biphasic infiltration (water plus air) in the network of penetrative structures from the overlying soil and host rock exercise remarkable control over the cave environment, delaying the thermal response of the cave air to the outer climate-driven changes and also the gaseous transfer between the cave atmosphere and the exterior. The cave location concerning the karstified outcrop determines that this subterranean site acts as a gas emitter during summer, which is contrary to what happens in many other caves. Prominent gas entrapment at a micro-local level is also registered in some upper galleries.

The Cross of the Inquisition, sculpted in 1903 and raised on a column with a fluted shaft and ornamented with vegetable garlands, is located in a corner of the Plateresque façade of the Seville City Hall. The Cross was vandalized in September 2019 and the restoration concluded in September 2021. A geological and microbiological study was carried out in a few small fragments. The data are consistent with the exposure of the Cross of the Inquisition to an urban environment for more than 100 years. During that time, a lichen community colonized the Cross and the nearby City Hall façades. The lichens, bryophytes and fungi colonizing the limestone surface composed an urban community, regenerated from the remains of the original communities, after superficial cleaning of the limestone between 2008 and 2010. This biological activity was detrimental to the integrity of the limestone, as showed by the pitting and channels, which evidence the lytic activity of organisms on the stone surface. Stone consolidation was achieved with Estel 1000. Preventol RI80, a biocide able to penetrate the porous limestone and active against bacteria, fungi, lichens, and bryophytes, was applied in the restoration.

The sandstones which constitute the host rock for the prehistoric artwork in the Rock Groups of Tajo de las Figuras and Peñas de Cabrera (southern Spain) show a serious degree of alteration, due both to natural processes and those related to anthropogenic and animal activity. A detailed study was carried out on the petrological and compositional characteristics of the sandstones (fresh and altered rock) in both rock groups, and on the geological and climatological characteristics of the area in which they are located. The sandstones have very similar petrological and compositional characteristics in both areas. This likeness causes the nature of the natural weathering processes to be similar in the rock areas studied. These processes can be divided in terms of the predominant mecha nisms of alteration into three inter-related categories: mechanical weathering, chemical weathering, and bio-induced alteration processes. However, the different climatic conditions of the areas in which the two rock areas are located directly influences the intensity of these processes. The precipitation and the range of temperature variation with heavy winter frosts in the area of El Tajo de las Figuras are significantly higher than in the area of Peñas de Cabrera; this translates into a higher rate of weathering at El Tajo de las Figuras. Regarding the anthropogenic action, two types of influence on the deterioration can be distinguished: a direct one, which consists of scouring and wetting of the walls in order to increase the chromatic contrast; and an indirect one, which is the extraction of blocks of sandstone in the upper part of rock shelters, which in turn encourages the development of the chemical weathering processes.

At the unique site of El Sidrón there have been an impressive series of events related to the activities and behaviors of the Neandertal species, integrated into peculiar environmental processes, seasoned with the proximity of the best Asturian siliceous raw material, and with a peculiar chain of expeditious and fast situations. All this integrated into an interdisciplinary investigation, En el singular yacimiento de El Sidrón se han producido una impactante serie de acontecimientos relacionados con las actividades y comportamientos de la especie neandertal, integradas en unos procesos del medio físico peculiares, sazonadas con la proximidad de la mejor materia prima silícea asturiana, y con un peculiar encadenamiento de situaciones expeditivas y rápidas. Todo ello integrado en una investigación interdisciplinar